I would recommend that the nose of the bullet just enters the chamber when the base of the cartridge case leaves the belt link. The longer 7.62x51 case should put the base farther back than with the 7.63x39 so the feeding angle will be less anyway. Cntrailrider has had success with his feed tray farther back than mine though but you have to have the bolt traveling forward fast enough to throw the round into the chamber if it is mid air when it leaves the belt link and before it enters the chamber.

Lookin' real good. Not a good idea to have cartridges flying through the air (unsupported). Almost nosing in the chamber as it's leaving the link is best, and the path always seems rather steep. Height of your feed tray is critical, to overcome the steep angle.

GOt the lower rails made, the bolt is sliding as well as the barrel back on today. I sure do love this "screw build" and being able to take it apart and put it back together over and over. I may never smush a rivet again.